Heater system

ABSTRACT

A heater system comprising a reaction vessel having a liquid metal mixture and a container of oxidant communicating therewith via a regulating valve. The oxidant reacts with the metal melt exothermically producing solid and/or liquid reaction products. The system furthermore comprises a spare container filled with the same metal mixture, this spare container being in heat contact with the reaction vessel and in communication with said vessel through a supply duct and removal duct; pumping means are present for maintaining a continuous liquid flow from the reaction vessel to the spare container, all this in such manner that the formed reaction products settle in the spare container.

United States Patent Schroder 1 May 16, 1972 [54] HEATER SYSTEM 3,367,; 19 2/1968 Caner, Jr 126/204 3,385,286 5/1968 Jones ...l26/204 [72] Aachen Gemany 3,450,127 6/1969 HaI'WOOd, Jr. ..126/204 [73] Assignee: U.S. Philips Corporation, New York, N.Y.

Primary Examiner-Charles J. Myhre [221 F1|ed= P 1969 Attorney-Frank P. Trifari 21 A LN 860 893 1 PP 0 t 57] ABSTRACT A heater system comprising a reaction vessel having a liquid [30] Fol-clan. Apphcauon Pnomy Dam metal mixture and a container of oxidant communicating Sept. 30, 1968 Netherlands ..68l3988 therewith via a regulating valve. The oxidant reacts with the metal melt exothermically producing solid and/or liquid reac- [52] U.S. Cl ..126/263 n products. Th y em f r h m r mpri a p re con- 51 1. 1 24 1 00 tainer filled with the same metal mixture, this spare container 58 Field of Search 126/263, 204; 165/46 being in heat Contact with the reaction vessel and in Communication with said vessel through a supply duct and removal [56] Reerences Cited duct; pumping means are present for maintaining a continuous liquid flow from the reaction vessel to the spare container, all UNITED STATES PATENTS this in such manner that the formed reaction products settle in the spare container. 3,161,192 12/1964 McCormack ..l26/204 3,229,681 1/1966 Gluckstein.... 1 26/204 7 Claims, 3 Drawing Figures 15 l xd ll 14 a 5 Cf 30 10 a w 1 I PfA'TENTEDm Is 1912 f I g .2

INVENTOR. JOHANN SCHRODER w BY AGEN

PATENTEDMM 16 I912 3.662.740

SHEET 2 [1F 2 INVENTOR. JOHANN SCHRODER Zmwa AGEN The invention relates to a heater system,- particularly for the supply of heat to a heat exchanger in which a medium flows. This system comprises at least one reaction vessel containing a metal or a mixture of metals which is liquid at" the operating temperature, and at least one container of anoxidant which is capable of reacting chemically and exothermically' with the liquid in the reaction vessel in such'manner that the reaction products are solid and/or liquid atthe temperature andpressure prevailing in the reaction vessel.-The containercommw nicates communicating via at least one supply duct with the reaction vessel, and the system comprises a control .device for metering the supply of oxidant to the reaction vessel, the system furthermore comprisingat least one'pumping device for circulating the liquid in the reaction vessel.

Heater systems ofthe above-describedtypeare known and have the advantage of supplying heat independcntlyof the surroundings in which they are situated. In other words, said heater systems supply heat without consuming .air of combustionand without giving off .gasesof combustiongthus they are excellently suitable for use in places where noair ofcombustion is present or in places where pollution of air .is undesirable or inadmissible.

Heater systems of the type to which thepresent invention relates may beused for the supply of heat to engines in which a working medium traverses a thermodynamiccyclebetween an expansion space which is ata high temperature and a compression space which is at a lowtemperature. Examples of such engines are hot-gas engines, gas turbines, thermoelectric generators. The supply of heat from the heater system to-the engine may take placeby contacting the heater of the engine, which usually will be a pipe heater through which the working medium flows on its way to and from the expansion space, with the liquid in the reaction vessel. If desirable, the heat transfer from the reaction vessel to the heater may also take place with a heat-transportingmedium, for example, liquid NaK, which circulates in a system of pipes which isin heat exchanging relationship on onesidewith the reaction vessel and on the other side with theheater.

The metal or mixture ofmetals in the reaction vessel may be constituted by oneor more oflthe metalsLi, Ca, Na, K, Mg, Al and/or one or more of the rare earth metals. These metals and especially combinations of said metals have the advantage of a.

comparatively low melting temperature and a large heat evolution per unit by volume. The oxidant may be-formed by a halogen or a halogen compound, particularly fluorine or a fluorine compound. The oxidant is suppliedto the reaction vessel in'dosed quantities, the oxidant reacting with the metal while evolving heat. Salts are formed which are solid and/or liquid at the operating temperature;

In the known systems the formed salts may give rise to two difficulties. in the first place the concentration of these salts in the reaction vessel constantly increases during operation and hence the metal concentration decreases so that the conversion rate decreases and the heat evolution occurs more slowly as more salts are formed. Secondly the formed salts or salt mixtures generally have a higher melting point than the metals or metal alloys. The result of this is that said salts or mixtures of salts tend to deposit at colder places. Since the colder place ismainly formed by the heat-exchanger (heater) in which heat is withdrawn from the liquid in the reaction vessel, the formed salts or mixture of salts will deposit on the pipes of the heat exchanger. As a result these pipes are provided with a heat insulating layer which, of course, is extremely undesirable. Further difficulty. occurs in that the formed salts or mixtures of salts, due to their larger specific gravity and lower miscibility with the liquid metal, tend tosettleat undesiredplaces in:the reaction vessel and'thus clog the ducts.

It is the object of the invention'tomitigatethe above-mentioned drawback; the invention is characterized in that the heater system comprises at least one spare container which is filled at least partly with thecsame-metal or the same-mixture of metals as the reaction vessel. The container is in heatexchangingcontact with a heat source;and the reaction vessel and the spare container communicatewith each other via a liquid supply duct and a liquid outlet duct. The pumping device and/or a further pumping. device maintain a flow of liquid from the reaction vessel to the spare container and back during operation, in-suchmannerthat the'rate of flow'in the reaction'vessel-is' larger than in the'spare container.

Anadvantage of the system'accoiding to theinvention is that only a small-part of the totalquantity of metal ormixture of metals which ispresent in the system ispresent in the'reaction vessel. This means that the-supply of heat can very-rapidly be started because for'this'purposeonly the reaction vesselhas to be brought to the melting temperature, after which the gaseousoxidant can be supplied and the reaction starts. While the whole flow ofliquid supplied by the pump orpumps passes both the reaction vessel and'thespare container, and it also possible to conduct the total supplied flow of liquid through the reactionvessel and. then a part through the spare container, while the other part flows back'directly to the suction side of the pump. In both manners there is achieved a flow of liquidof a high concentration of salts constantly from the reaction vessel tothe spare container, while a flow of liquid having a low concentration of salts is conducted from the spare container to the reaction vessel. Since the liquid in the spare container flows comparatively slowly, the salts, due to their larger specific gravity, will settle in the spare container. in this manner the salt concentration in the reaction vessel remains low, so that the reaction conditions for oxidant and metal are and remain as favorable as possible. Furthermore the saltsformedby the reaction as a result of the rapid flow in the reaction'vessel will occur in the liquid in a finely dispersed condition. As a result of this, said salts will have no opportuni ty of depositing oh the heat exchanger pipes so that always a good heat passage is ensured.

In afurther favorable embodiment of the system according to the invention, the heat source'for heating the spare container is formed by the reaction vessel. The heat transfer can take place by the continuous flow of liquid from the reaction vesselto the spare container. Also it is possible to use a further heat transport system for the transport of 'heat from the reaction vessel to the spare container.

in another favorable embodiment ofthe system the reaction vessel comprises a heat transmitting wall incorporated in the spare container. In this embodiment, heat will flow directly from the reaction vessel to the spare container.

Another embodiment of the heater system in which the reaction vessel is constructed as a circulation channel in which a pumping device is incorporated for circulating the liquid, is characterized in that the liquid outlet duct and the liquid supply duct communicate with the channel at places of different pressures, said places viewed in the direction of circulation of the liquid, being situated one behind the other and preferably communicate with the part of the duct communicating with the outlet side of the pump and the part of the duct communicating with the suction side of the pump, respectively. In this embodiment a part of the liquid flowing through the reaction vessel will continuously flow back to the spare container due to the differential pressure between the outlet and supply ducts. I

In a further favorable embodiment the spare container at room temperature is partly filled with metal or a mixture of metals while at the operating temperature saidcontainer is substantially entirely filled due to the thermal'expansion only. A gas is presentin the'free space in the spare container above the metal,-which gas is inert tothe metal or mixture of metals.

Also present are means to maintain said gas at a given pressure, in which at least the supply duct opens at a level in the container which lies only slightly below the liquid level at the operating temperature, and in which sealing means are present to close the outlet duct until the operating temperature is reached. By closing the outlet duct until the operating temperature is reached, there is no danger that the reaction vessel is pumped empty during the starting period. Since the supply duct is in open communication with the gas space in the spare container, the initial filling of the reaction container is not critical. In the case of an excess ofliquid, due to the expansion, the liquid can escape to the spare container through the supply duct. All this is constructed so that at the operating temperature both the orifice of the supply duct and that of the outlet duct in the spare container lie below the liquid level so that a circulation of liquid occurs as soon as the passage of the outlet duct is released.

In a further favorable embodiment the outlet duct opens into the spare container, its orifice being closed by a plate of material which melts and/or dissolves a short period of time prior to reaching the operating temperature.

In order to prevent the liquid from rocking strongly in the spare container, for example, when the heater system is used in vehicles, with all the undesirable consequences of this, the spare container may be divided into compartments by a number of partitions which extend from the bottom to slightly below the liquid level.

In order that the invention may be readily carried into effeet, a few examples of heater systems will now be described in greater detail, by way of example with reference to the accompanying diagrammatic drawings which are not drawn to scale and in which FIGS. 1, 2, and 3 diagrammatically show not to scale three embodiments of heater systems in which, by way of example, the evolved heat is transferred to the heater of a hot-gas engine.

Referring now to FIG. 1, reference numeral 1 denotes a reaction vessel which is filled with a mixture of metals, substantially Li and Ca. Reference numeral 2 denotes a container containing an oxidant, for example, SF which can react with the metal mixture in the reaction container 1 for evolving heat. The container 2 communicates with the reaction container 1 via a regulating valve 3 and a number of oxidant supply ducts 4 of which two are shown in the drawing. Reference numeral 5 denotes a spare container which contains the same metal mixture as the reaction vessel. The spare container communicates, via an outlet duct 6 in which a pump 7 is incorporated with the reaction vessel 1. The spare container 5 furthermore communicates with the reaction vessel 1 by means of a supply duct 8. The outlet duct 6 opens into the upper side of the spare container 5, while the supply duct 8 opens below the liquid level at operating temperature. The heater system furthermore comprises a container 10 containing an inert gas, for example, He or Ar. This container 10 communicates, via a gas supply duct 11, at the area 12 with the supply ducts 4. In the supply duct 11 a regulating valve 13 is provided. The container 10 furthermore communicates, via an outlet duct 14 with regulating valve 15 and compressor incorporated therein, with the spare container 5. A stirrer 18 coupled to an electric motor 19, is immersed in the reaction container 1. A heater 20 of a hot gas engine 21 is arranged in the reaction vessel 1. This heater comprises a number of pipes 22 arranged in a ring which communicates at one end with the regenerator 23 of the hot-gas engine 21, and at the other end with an annular duct 24, and comprises a number of pipes 25 which communicate the annular duct 24 with the expansion space 26 of the hot gas engine.

The operation of this system is as follows: Initially the whole system is at the ambient temperatures so that the metal in the reaction vessel 1 and the spare container Sis solid. In order to enable the reaction in the reaction vessel 1, the metal mixture should first be melted, so that oxidant can then be introduced into the reaction vessel 1 from the container 2 via supply ducts 4. The heating to melting temperature occurs by means of electric heating devices 30. Simultaneously with the heating devices 30, the heating devices 31 in the spare container 5 are energized. Since the quantity of metal in the reaction container is small with respect to that present in the spare container 5, the reaction vessel will reach its temperature far more rapidly than the spare container. This means that the reaction can rapidly be started in which, due to the supply of SP to the reaction vessel 1 dosed by means of the regulating valve 3, a chemical reaction occurs between the oxidant and the metal, during which thermal energy is liberated. This thermal energy is transferred to the working medium which flows through the heater 20 of the hot-gas engine. In order to obtain a good contact between the liquid metal and the heater pipes 22 and 25, a stirrer 18 is arranged in the reaction vessel 1 and is started as soon as the metal is liquid. As a result of said stirring, the metal comes in a good contact with the heater pipes, so that a good heat transfer is obtained.

The reaction vessel contains a quantity of mixture such that at the operating temperature, the vessel is just filled with liquid due to the thermal expansion. Any excess can flow away via the ducts 6 or 8 to the spare container. The spare container 5 contains a quantity of metal mixture, such that at the operating temperature, this container is also substantially filled with liquid, while the small space above it is filled with inert gas, for example, Ar, from the container 10. This gas from the container 10 is supplied to the ducts 4, via duct 11, the supplied quantity being regulated by means of the valve 13 in such manner that such a large flow of gas occurs through the ducts 4 that no liquid can enter the ducts 4. The inert gas supplied to the reaction vessel 1 can flow to the spare container 5, via the duct 6, and thence via duct 14, valve 15, and compressor 16 it can be returned to the container 10. At the instant the metal in the spare container 5 has also liquefied, the pump 7 is actuated. Due to the pumping action, a flow of liquid is obtained through duct 6 from the reaction vessel 1 to the spare container 5. A flow ofliquid also occurs through the duct 6 from the spare container 5 to the reaction vessel 1. The flow of liquid removed from the reaction vessel through the duct 6 will contain salts formed during the reaction in said container. These salts which are solid and/or liquid have a higher specific gravity than the liquid metal. Furthermore said salts show only a slight miscibility with the liquid metal. In the spare container the liquid flows at a low rate so that the salts obtain an opportunity of settling in said container. The flow of liquid which flows back to the reaction vessel via the duct 8 contains substantially no salt. In this manner an increase of the salt concentration in the reaction vessel is counteracted so that the reaction conditions are and remain favourable. A great advantage of this system is that the salts now obtain substantially no opportunity of depositing in a solid form on the heater pipes, so that the heat transfer always remains satisfactory.

During operation the electric heating devices need naturally not be energized. In the reaction vessel 1, a sufficient thermal energy is developed for maintaining the operating temperature, while a part of said energy is conducted with the liquid through duct 6 to the spare container 5, so that there the operating temperature is also maintained.

Melting of the metal mixture may occur, instead of electrically, by means of a burner or another chemical reaction, or by causing the hot-gas engine to operate temporarily as a heat pump.

Partitions 32 are provided in the spare container 5 so as to prevent the liquid therein from rocking too much as a result of shocks. These partitions may be perforated, if desirable.

FIG. 2 shows a slightly varied form of the heat system shown in FIG. 1. In this figure corresponding components are referred to by the same reference numerals. The reaction vessel 1 has the form of a bypass having a heat transmitting wall which is accomodated in the spare container 5. The metal in the reaction vessel can again be melted by an electric heating device 30 or in any other suitable manner, if desirable. Oxidant, for example, SP can be introduced into the reaction manner that such a large flow of medium always occurs in the duct 4, that no liquid metal can enter it. A pumping device 35 coupled to an electric motor 36 ensures the circulation at high speed of the liquid in the bypass l. The container communicates, via the duct 14 with a compressor 16 incorporated therein and control valve 15, with the spare container 5. An outlet duct 6 and a supply duct 8 furthermore communicate with the bypass. These ducts communicate with places where different pressures-prevail during operation and that in such manner that the duct 6 communicates with a place having a higher pressure and duct 8 with a place having a lower pressure. The ducts 6 and 8 open into the spare container at a level which lies slightly below the liquid level at the operating temperature. Initially the duct 6 is closed by a plate of a material, for example, lanthanum (melting point 840 C) which melts shortly before reaching the operating temperature. If desirable said plate may be replaced by a controllable cock.

The heat evolved in the reaction container 1 is transferred to liquid NaK serving as a heat transporting medium which circulates in a system of ducts 40 and, at the area 41, becomes thermal energy from the reaction vessel and, at the area 42, supplies said heat to the heater of the hot gas engine 21. A pump 43 ensures the circulation of the NaK.

The operation of the heater system is as follows. First the metal in the bypass l is melted by means of the heating device 30. Then pump 35 is actuated and valve 3 is opened so that oxidant can enter. Due to the reaction, heat is evolved which is partly supplied to the hot gas engine and partly serves for bringing the metal in the spare container 5 at the desired temperature.

The bypass contains a quantity of metal mixture such that upon reaching the operating temperature, it is filled entirely due to thermal expansion. Furthermore the spare container contains a quantity of metal such that initially the orifices of the'ducts 6 and 8 lie in the gas space above it, while upon reaching the operating temperature, the liquid level lies above said orifices as a result of the thermal expansion. If duct 6 were not closed, liquid'would initially be removed from the bypass through said duct as a result of the action of the pump 35, while liquid cannot yet be supplied via duct 8. So the bypass would be emptied. By closing the duct 6 by means of a plate which melts. only a short time prior to reaching the operating temperature, said emptying -is prevented. Upon reaching the operating temperature the plate melts and liquid will now continuously flow via duct 6 to the spare container while via duct 8 said removed liquid is replaced by clean" liquid from the spare container. The salts removed from the bypass with the flow of liquid through the duct 6 will settle in the spare container 5. In this manner again a heater system having a short starting period is obtained, the liquid in the reaction vessel showing no increase in the concentration of salts.

FIG. 3 finally shows a heater system in which, as in FIG. 2, the reaction vessel 1 has the form of a bypass in which the heater 20 of the hot-gas engine 21 is provided directly in said bypass. The reaction vessel 1 is formed by a cylindrical container 50. In this container a second cylinder 51 is placed con-.

centrically with the cylinder 50, the cylinder 51 being open at either end and not touching the end walls of the cylinder 50. One end of the cylinder 51 communicates with the annular duct 24 of the heater 20 of the hot gas engine. This means that the ring of heater pipes 22 and 25 forms as it were, a continuation of the cylinder 51. On the other side an aperture 52 is present between the cylinder 51 and the end wall of the cylinder 50. In this manner a bypass is obtained in which the pump 35 is placed in the cylinder 51. As regards construction and operation, the further components correspond to those of the system shown in FIG. 2 so that they require no further description.

From the above it may be obvious that the invention provides an extremely readily operating heater system which operates independently of its surroundings, has a short starting period, and a regular removal of the formed salts from the reaction vessel.

What is claimed is:

l. A system for supplying heat, comprising:

a. a reaction vessel,

b. aspare container, and inlet and outlet ducts communicating the vessel with the container, 7 c. a reaction material formed of at least one metal that is a liquid in the operating temperature range of the system, some material in said vessel, the remaining material in the spare material,

. means containing an oxidant conveyable to the vessel for reaction with said liquid reaction material producing reaction products in the vessel which may include liquid and solid,

e. a supply duct for conveying oxidant from the first container to said vessel,

. means for controlling the quantity of oxidant conveyed,

and

g. pump means for circulating liquid in the system,

. heat source means for providing heat to the vessel and the spare container and reaction material therein, for initiating operation of the system, whereby reaction products are conveyed out of the vessel to the spare container, and reaction material is conveyed from the spare container to the vessel, with the'flow rate in the vessel being greater than in the spare container.

2. A heater system according to claim 1, wherein the heat source means for the spare container comprises a portion of said vessel in heat exchanging relationship with the container.

3. A heater system according to claim 2 wherein the heat source formed by the reaction vessel, comprises heat transmitting wall incorporated in the spare container.

4. A heater system according to claim 1 wherein the reaction vessel is constructed as a circulating channel having locations at different pressures, the pumping means is incorporated therein with the liquid outlet duct and the liquid supply duct communicating respectively (i) with said places of different pressures in the channel, and (ii) with the outlet side of the pump and the suction side of the pump.

5. A heater system according to claim 1, wherein the spare container at room temperature is partly filled with reaction material and at the operating temperature said container is substantially entirely filled due to thermal expansion, the space above the material in the spare container containing a gas inert to the material, the system further comprising means for maintaining said inert gas at a selected pressure, the supply duct opening being at a level in the spare container which is situated only slightly below the liquid level at the operating temperature, and sealing means for closing the outlet duct until the operating temperature is reached.

6. A heater system according to claim 3 wherein the outlet duct is situated at substantially the same level as the supply duct in the spare container, its orifice being closed by a plate of a material which, shortly prior to reaching the operating temperature, melts or dissolves.

7. A heater system according to claim 1 wherein the spare container is divided into compartments by partitions which extend from the bottom to slightly below the liquid level. 

2. A heater system according to claim 1, wherein the heat source means for the spare container comprises a portion of said vessel in heat exchanging relationship with the container.
 3. A heater system according to claim 2 wherein the heat source formed by the reaction vessel, comprises heat transmitting wall incorporated in the spare container.
 4. A heater system according to claim 1 wherein the reaction vessel is constructed as a circulating channel having locations at different pressures, the pumping means is incorporated therein with the liquid outlet duct and the liquid supply duct communicating respectively (i) with said places of different pressures in the channel, and (ii) with the outlet side of the pump and the suction side of the pump.
 5. A heater system according to claim 1, wherein the spare container at room temperature is partly filled with reaction material and at the operating temperature said container is substantially entirely filled due to thermal expansion, the space above the material in the spare container containing a gas inert to the material, the system further comprising means for maintaining said inert gas at a selected pressure, the supply duct opening being at a level in the spare container which is situated only slightly below the liquid level at the operating temperature, and sealing means for closing the outlet duct until the operating temperature is reached.
 6. A heater system according to claim 3 wherein the outlet duct is situated at substantially the same level as the supply duct in the spare container, its orifice being closed by a plate of a material which, shortly prior to reaching the operating temperature, melts or dissolves.
 7. A heater system according to claim 1 wherein the spare container is divided into compartments by partitions which extend from the bottom to slightly below the liquid level. 